1. Field of the Invention
This invention is directed to a catalyst using subnanometer to nanometer sized clusters of atoms to facilitate chemical reactions, and more specifically, the invention is directed to a method for using all atoms within a catalyst cluster to efficiently convert reactants to desired product.
2. Background of the Invention
The catalytic oxidation of carbon monoxide (CO) to carbon dioxide (CO2) is important in the automotive industry for pollution control and for the development of hydrogen fuel cells. In terms of pollution control, large amounts of carbon monoxide lead to the formation of ground level smog and ozone, which can cause respiratory problems for some people. In hydrogen fuel cells using a proton exchange membrane (PEM), carbon monoxide impairs the operation of the PEM at concentrations higher than 10 ppm. Platinum catalysts are used in these applications to remove carbon monoxide from the systems by transforming it into carbon dioxide, thus avoiding said pollution and PEM impairment issues.
Platinum is perhaps the best catalyst for the oxidation of CO. However, platinum is also very rare and, thus, relatively expensive compared to other catalyst metals, like silver or palladium. Accordingly, catalysts using platinum metal are also expensive.
Many conventional catalysts, such as might be found in a catalytic converter, use large deposits or films of platinum to facilitate the CO oxidation reaction. However, the films and deposits contain several platinum atoms in the interior of the bulk structure. These atoms do not participate in the oxidation reaction and, therefore, are wasted in the catalyst. By incorporating a large number of non-participating platinum atoms in the catalyst, the cost of the catalyst is needlessly increased.
In response, recent work has focused on catalytic nanoclusters as a means to reduce the amount of catalyst material necessary to facilitate certain reactions. Nevertheless, clusters of appropriate size and combinations of substrate and support material have not been identified to enhance the efficiency and cost-effectiveness of platinum catalysts for CO oxidation.
In order to lower the cost of oxidation catalysts, especially those using platinum, it is desirable to use the least amount of platinum possible while maintaining the highest level of reactivity. Thus, a need exists in the art for a catalyst with such properties.